I think that the disillusion comes in when we forget that it's simply an illusion and we start mistaking it for reality. A telephone game of sorts, in my own life I call this the "Phil Collins Is Coming" theorem. Named appropriately after a time in my youth when a simple remark about Phil Collins later turned into rumors spread of an upcoming concert (not true) as it traveled through various sources and morphed along the way. By the end, even the original remark maker was convinced of the truth of the event, although it was all for naught.

I think it, therefore it is. Or, I think it so much that I forget it is not except in my own head.